Hello ,
This is because both the VPN gatways are using ISP 1 by taking the default route :
route 0.0.0.0/0 next-hop 1.1.1.1;
So create 2 routes :
5.5.5.5 next hop ISP1
6.6.6.6 next hop ISP 2
This will make the secondary ISP/VPN UP even when first ISP is down .